When a node of the treeview (in a combobox) is clicked, the text and value of this node is set to the selected item of the combobox. client side this works well. serverside the selectedvalue is rondomly empty.

function nodeClicking(sender, args) {

var comboBox = $find("<%= cbEmployees.ClientID %>");

var node = args.get_node()

comboBox.set_text(node.get_text());

comboBox.trackChanges();

var item = comboBox.get_items().getItem(0);

item.set_value(node.get_value());

item.set_text(node.get_text());

comboBox.commitChanges();

comboBox.hideDropDown();

comboBox.attachDropDown();

}